'''Graham Morrison decodes the secret meaning behind the most common Linux error messages and helps you cure the problems in the process.'''

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''Original version written by Graham Morrison in LXF 109 (September 2008). For the original article in PDF [[click here for .pdf link]].

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'''Some people are scared of Linux because the error messages it produces seem to imply the coming of the apocalypse. And there’s a great number of them. If you search for the word ‘Error’ in our forums, you get more than 150 pages of results. That’s a lot of people experiencing a lot of problems.'''

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The biggest difficulty for these users isn’t the

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number of error messages; it’s trying to get

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something useful out of them. What does ‘Kernel

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Oops’ mean, for example, or ‘PCI Can’t Allocate’?

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Linux error messages are obtuse, difficult to

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understand and rarely helpful. Which is a pity,

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because the vast majority of problems can be

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solved quite easily, and a considerable number

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involve the same problems recurring again and

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again. In business speak, these are low-hanging

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fruit. And it’s these problems we want to target.

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You shouldn’t need to be a Linux expert to get

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your machine to boot, or a programmer to play a

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movie file. Yet it’s this level of expertise that most

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error messages seem to assume of their users. We

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want to demystify these common errors, and

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provide solutions that should help ordinary Linux

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users side-step the problem and get their machine

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back on track. We’ve chosen areas we think are

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the most problematic. These include booting

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problems, general software usage, the filesystem,

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networking and distro installation.

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We’ve picked a few of the most common errors

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from each, and explained what’s happening along

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with the solution. The intention is that even if the

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problems don’t apply to you, you can get an idea

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of how and why Linux error messages might seem

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arcane and a little intimidating. And hopefully,

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this will leave you with the knowledge to find a

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better solution that might help you to solve your

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own problems.

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== Distro installation ==

== Distro installation ==

'''Every Linux distribution has a different installation routine, and each creates problems. Ubuntu might work for one machine and not for another. A machine with a working Ubuntu installation may not work with Fedora, or OpenSUSE, or Linux Mint, or Mandriva...'''

'''Every Linux distribution has a different installation routine, and each creates problems. Ubuntu might work for one machine and not for another. A machine with a working Ubuntu installation may not work with Fedora, or OpenSUSE, or Linux Mint, or Mandriva...'''

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* '''ERROR Can’t boot from CD/DVD'''

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=== '''ERROR: Can’t boot from CD/DVD''' ===

If you’re new to Linux, this is often your first experience of the

If you’re new to Linux, this is often your first experience of the

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find yourself in an internet cafe or in front of a corporate machine.

find yourself in an internet cafe or in front of a corporate machine.

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* '''ERROR PCI: cannot allocate'''

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=== '''ERROR: PCI: cannot allocate''' ===

There are many errors like this, and they mostly occur at boot

There are many errors like this, and they mostly occur at boot

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problems, and if you go on to install Linux, your distro should make

problems, and if you go on to install Linux, your distro should make

a better job of choosing the correct drivers for the installation.

a better job of choosing the correct drivers for the installation.

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== Booting problems ==

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'''There’s nothing worse than an error that stops your system booting – mainly because you’re now without your primary problem solving tool. Yet booting problems are common. This is because we all like to install distributions, and we often run more than one on a single machine, as well as share a hard drive with Windows. Any one of these installations can mess up the boot routine, and getting a working installation back isn’t always so easy.'''

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* '''ERROR Grub...'''

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If this is all you see when you turn on your machine, the Grub boot

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menu has been corrupted. This is the part of your Linux

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installation that’s responsible for booting the operating system.

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And the only thing you can do is boot Linux off some other media,

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preferably a Live Linux CD. When you get to the desktop, open a

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command line terminal, switch to the administrator account and

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type '''grub'''. This next step will also work if your Grub menu entries

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no longer point to your Linux partition.

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Type '''find /boot/grub/stage1'''. This is searching for the

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location of the original boot drive, and it should return something

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along the lines of '''(hd0,0)''' – this is ''Grub''’s own syntax for the

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location of the hard drive, and this is dependent on your own

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installation, so don’t assume it’s going to be '''(hd0,0)'''. You should

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now type root '''(hd0,0)''' (or your equivalent) to tell Grub which

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partition is being used to boot from, followed by '''setup (hd0)''' to

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reinstall the boot loader into the disk’s master boot record. You

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should then be able to restart your machine and boot normally.

Current revision

Distro installation

Every Linux distribution has a different installation routine, and each creates problems. Ubuntu might work for one machine and not for another. A machine with a working Ubuntu installation may not work with Fedora, or OpenSUSE, or Linux Mint, or Mandriva...

ERROR: Can’t boot from CD/DVD

If you’re new to Linux, this is often your first experience of the
operating system: you insert your new disc into the drive and
restart the machine, only to be greeted by the same operating
system you were using before. The problem is that your hard drive
has a higher boot priority than your optical drive. Many modern
BIOSes include a boot menu from where you can change the
priority of your devices on the fly – try pressing the ‘Escape’ key or
F12 when you first see something on the screen. From there, you
can simply choose to boot from the optical drive.

Older machines might not have the same facility. You will then
need to press either the F2 or ‘Del’ key at boot time to enter the
system BIOS, and change the boot order from there. You can
usually find the option under the ‘Boot’ menu, and you will need to
save these changes to be able to boot from the optical drive. This
is the same procedure you would use if you needed to boot from
an external drive or USB stick, which can be just as useful if you
find yourself in an internet cafe or in front of a corporate machine.

ERROR: PCI: cannot allocate

There are many errors like this, and they mostly occur at boot
time. They all share the same cause – badly behaved power
management. The culprit is something called ACPI, the Advanced
Configuration and Power Interface. Despite being a standard for
power management, it has been causing problems for over ten
years. The trouble is that hardware drivers have a habit of not fully
implementing the specification. Whenever your machine’s power
management spins into action, such as when you turn on your
machine, or resume from sleep, certain devices cause problems.
Live CD installations make this problem worse, because they don’t
have the luxury of probing for exact hardware matches when they
boot, or including every possible driver for every device, which is
why this problem often occurs when installing off a Live CD.

There’s only one thing you can do – turn off ACPI. You can
sometimes do this from your system BIOS, but if not, you’ll need
to disable ACPI at boot time. Press Escape when booting to enter
the Grub menu and select the option you normally use. Go down
to the line that starts with kernel and press E to edit the line. At the
end of this line add acpi=off noapic, press return and B to start
the boot process. You should find that your machine boots without
problems, and if you go on to install Linux, your distro should make
a better job of choosing the correct drivers for the installation.